The ornamental design for a vent cover, as shown and described.
FIG. 1 is a front perspective view of one preferred embodiment of the vent cover of the present invention as the same could be coupled to the roof of a structure;
FIG. 2 is a top plan view of the vent cover depicted in FIG. 1;
FIG. 3 is a rear elevation view of the vent cover depicted in FIG. 1;
FIG. 4 is a side elevation view of the vent cover depicted in FIG. 1;
FIG. 5 is a front elevation view of the vent cover depicted in FIG. 1; and,
FIG. 6 is a bottom plan view of the vent cover depicted in FIG. 1.